The present invention relates to a transmission power control circuit, and more particularly, to a transmission power control circuit controlling a transmission power of a transmitting wave using a detector.
Generally, in a prior art wireless terminal apparatus such as a portable telephone, a feedback control using a detector was performed to control a transmission power of a transmitting wave output.
Referring to FIG. 24, a transmission power control circuit 10 according to a prior art technique included: a variable gain amplifier 1; a distributor 2; a detecting circuit 3; a reference voltage generating circuit 4; and a power control section 5.
Variable gain amplifier 1 amplifies a transmission signal with a gain according to a given control voltage VC to generate a transmitting wave output. Distributor 2 takes out part of a transmission power POUT of a transmitting wave output. Detecting circuit 3 detects part of the transmission power obtained by distributor 2 and generates a detection voltage VDET according to transmission power POUT. That is, detection voltage VDET changes according to transmission power POUT.
Reference voltage generating circuit 4 generates a reference voltage VREF corresponding to a designated level of transmission power POUT. Power control section 5 generates control voltage VC according to a negative-fed back voltage K0xc2x7VDET obtained by multiplying detection voltage VDEF from detecting circuit 3 by a detection voltage feed-back ratio K0, and to VREF from reference voltage generating circuit 4, based on the following equation (1).
VC=VREFxe2x88x92K0xc2x7VDETxe2x80x83xe2x80x83(1)
By detecting part of transmission power POUT of a transmitting wave output using distributor 2 and detecting circuit 3 in such a way to further apply negative-feedback, there can be performed close loop control to cause transmission power POUT and a designated value PCMD of transmission power to coincide with each other.
To be concrete, in a case where transmission power POUT is higher than a designated level, detection voltage VDET becomes higher to, in response to this, lower control voltage VC outputted from power control section 5. As a result, a gain of variable gain amplifier 1 is set small, which works so as to reduce transmission power POUT. To the contrary, in a case where transmission power POUT is set to a value lower than a designated value, in response control voltage VC is set high, which works so as to raise transmission power POUT to be large. By performing such a close loop control, control can be executed so that an error between transmission power POUT of a transmitting wave output and a designated level is reduced to the least possible value.
Referring to FIG. 25, reference voltage generating circuit 4 includes a transmission power designating section 7; a control section 8; and D/A converter 9. Transmission power designated value PCMD indicating a designated level of a transmission power is converted to reference voltage VREF by control section 8 and D/A converter 9. That is, reference voltage VREF is set in correspondence to transmission power designated value PCMD.
Power control section 5 includes: an operational amplifier 10; and resistance elements 11 and 12. Detection voltage VDET from detecting circuit 3 is transmitted to a node N0 corresponding to the inverted input terminal (xe2x88x92terminal) of operational amplifier 10 through resistance element 12. Reference voltage VREF from D/A converter 9 is inputted to the non-inverting input terminal (+terminal) of operational amplifier 10. Resistance element 11 is coupled between the inverted input terminal and the output terminal of operational amplifier 10. Therefore, detection voltage feed-back ratio K0 shown in FIG. 28 is determined according to a ratio between resistance elements 11 and 12.
In such a way, in an architecture of transmission power control circuit 10 according to a prior art technique, it was a precondition that detecting circuit 3 can output a detection voltage corresponding to a transmission power all over a dynamic range of transmission power POUT. However, in a case where a dynamic range of transmission power is set wide, generally, it is rather difficult to broaden a measurable range of detecting circuit 3 than to broaden a dynamic range of a gain of variable gain amplifier 1. With a wider measurable range of detecting circuit 3, a detecting circuit tends to become complex and up-scaled, resulting in a high cost.
It is an object of the present invention is to provide a transmission power control circuit capable of ensuring a wide dynamic range of transmission power using a general inexpensive detecting circuit having a simple architecture.
According to the present invention, a transmission power control circuit includes: a variable gain amplifier for amplifying a transmission signal with a gain according to a control voltage to output a transmitting wave; a distributing section for taking out part of the transmitting wave; a detecting section for detecting an output of said distributing section to generate a detection voltage corresponding to a transmission power of the transmitting wave; and a control section receiving an electrical signal indicating a designated level of the transmission power and the detection voltage to set the control voltage. The control section performs a changeover between a first control state setting the control voltage by close loop control according to the detection voltage negative-fed back, multiplied by a feedback ratio and a reference voltage corresponding to the designated level, and a second control state setting the control voltage by open loop control according to the designated level, according to a relationship between a measurable power range of the detecting section and the transmission power.
The control section preferably performs the changeover between the first and second control states according to the detection voltage.
Furthermore, the control section preferably performs the changeover between the first and second control states according to a designated level of the transmission power.
Moreover, the control section preferably includes: a first signal converting section converting a detection voltage to a first digital signal; a control computing section receiving a second digital signal indicating a designated level of a transmission power and the first signal to perform a digital computing for setting a control voltage based on one of the first and second control state, which is selected according to comparison between the first and second digital signals; and a second signal converting section converting an output of the control computing section to an analog signal to generate the control voltage.
In such a transmission power control circuit, relationships between a designated level of a transmission power and a reference voltage are not set separately inside and outside a measurable range of the detecting circuit but a dynamic range of a transmission power can be widely ensured using a detecting section with a general architecture.
Furthermore, the control section preferably includes: a feedback ratio adjusting section for gradually reducing a feedback ratio from a prescribed level as a transmission power comes closer to a non-measurable power range in a prescribed boundary range between a measurable power range and non-measurable power range of a detection section in the first control state.
As a result, a sudden change can be prevented in a transmission power in a prescribed boundary range corresponding to a changeover region between the first control state and second control state.
The feedback ratio adjusting section more preferably changes a feedback ratio according to a detection voltage.
The feedback ratio adjusting section more preferably changes a feedback ratio according to a designated level of a transmission power.
The control section more preferably further includes: a first signal converting section converting a detection voltage to a first digital signal; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a first digital signal to perform a digital computing for setting a control voltage based on a feedback ratio set according to the second digital signal.
According to the present invention, the transmission power control circuit includes: a variable gain amplifier amplifying a transmission signal with a gain according to a control voltage to output a transmitting wave; a plurality of distributing sections for taking out part of the transmitting wave; and a plurality of detecting sections, provided corresponding to each of the plurality of distributing sections, respectively, and having different measurable power ranges. The plurality of detecting sections detect outputs of the corresponding distributing sections to generate a plurality of detection voltages according to a transmission power of the transmitting wave. The transmission power control circuit further includes: a control section receiving an electrical signal indicating a designated level of a transmission power and a plurality of detection voltages to set a control voltage. The control section includes: a feedback ratio control section setting a plurality of feedback ratios corresponding to the plurality of detection voltages, respectively, according to a relationship between the measurable power ranges of the plurality of detecting sections and a transmission power. The control section sets a control voltage according to close loop control based on a plurality of detection voltages negative-fed back multiplying each of the plurality of feedback ratios and a reference voltage corresponding to a designated level of a transmission power.
The measurable power ranges of at least part of the plurality of detecting sections preferably share an overlapped range between any two and the feedback ratio control section, when the transmission power of a transmitting wave corresponds to an overlapped range, sets the feedback ratios so that the detecting voltages from the detecting circuits sharing the overlapped range are synthesized and negative-fed back.
The feedback ratio control section, when the transmission power of a transmitting wave corresponds to an overlapped region, sets a plurality of feedback ratios so that a synthesis ratio between the plurality of detecting voltages to be synthesized gradually change according to the transmission power.
Such a transmission power control circuit can implement close loop control with a detective voltage in order to ensure a dynamic range of a transmission power to be wide without increasing a measurable range of each of the plurality of detecting sections, that is by using a plurality of common inexpensive detecting sections. Furthermore, a discontinuous change in transmission power can be prevented in changeover between mainly used detecting circuits according to a relationship between a measurable range of each of the detecting circuits and a detection voltage.
The feedback ratio adjusting section preferably sets a plurality of feedback ratios according to a plurality of detection voltages.
Furthermore, the feedback ratio adjusting section preferably sets a plurality of feedback ratios according to a designated level of a transmission power.
The control section preferably further includes: a first signal converting section for converting a plurality of detection voltages to a plurality of first digital signals; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a plurality of first digital signals to perform a digital computing for setting a control voltage based on a plurality of feedback ratios set according to a plurality of second digital signals.
The control section, when a transmission power does not belong to any of the measurable power ranges of a plurality of detecting sections, preferably temporarily ceases close loop control and sets a control voltage based on open loop control corresponding to a designated level of a transmission power.
Such a transmission control circuit can further control a transmission power based on open loop control of the transmission power at a designated level of transmission power in a range in which the transmission power does not correspond to any of measurable ranges of a plurality of detecting sections. Therefore, a transmission power can be stably controlled without setting relationships between a designated level of a transmission power and a reference voltage separately inside and outside a measurable range of a detecting circuit.
When an actual transmission power POUT belongs to one of measurable ranges of detecting circuits, similar to the transmission power control circuit according to the third embodiment, such a transmission power control circuit can implement close loop control with a detective voltage in order to ensure a dynamic range of a transmission power to be wide without increasing a measurable range of each of the plurality of detecting sections, that is by using a plurality of common inexpensive detecting sections. Furthermore, a discontinuous change in transmission power can be prevented in changeover between mainly used detecting circuits according to a relationship between a measurable range of each of the detecting circuits and a detection voltage.
The control section more preferably performs a changeover between close loop control and open loop control and setting of a plurality of feedback ratios in close loop control according to a plurality of detection voltages.
The control section more preferably performs a changeover between close loop control and open loop control and setting of a plurality of feedback ratios in close loop control according to a designated level of a transmission power.
The control section more preferably further includes: a first signal converting section converting a plurality of detection voltages to each of the plurality of first digital signals; and a second signal converting section converting an output of the feedback ratio adjusting section to an analog signal to generate a control voltage. The feedback ratio adjusting section receives a second digital signal indicating a designated level of a transmission power and a plurality of first digital signals to perform a digital computing for setting a control voltage using a plurality of feedback ratios set according to a plurality of second digital signals, based on one of open loop control and close loop control, which is selected according to comparison between first and second digital signals.